1. Technical Field
The invention relates to the field of high definition television signal transmission and, in particular, to the conversion and pre-processing of a high definition television signal prior to transmission.
2. Description of the Relevant Art
It is already fairly recognized that the Japanese Broadcasting Corporation (NHK) has pioneered a viable implementation of broadcasting high definition television signal images to a population of subscribers via its high definition 1125-line MUSE signal format. Japanese manufacturers have developed and are making commercially available studio camera and recording equipment and television receivers which conform to the MUSE standard. On the other hand, a high definition 1125 line 60 Hz field rate format is not easily transmitted over great distances, for example, by satellite, without expensive installation of complicated transmission and reception equipment or greatly increasing the signal bandwidth.
In the United States of America and in other countries as well, it has not been decided what high definition television signal format will eventually be selected as a national standard. However, it is clear that conservation of transmission bandwidth and backwards compatibility with existing National Television System Committee (N.T.S.C.) standards is at least desirable if not demanded. Furthermore, regardless of what format will be selected as a broadcast standard, there will be a need for another transmission format which lends itself to efficient transmission by satellite or other long distance transmission facilities.
A standard and high definition B-type multiplexed analog components (B-MAC) transmission format is known from prior United States patent applications of the present inventor. According to one high definition B-MAC transmission format, the signal employs the 0-10.7 MHz region of the transmitted spectrum. Nevertheless, a 525 line interlaced high definition television (HDTV) signal is output in addition to six audio outputs, teletext, optional data transmission and optional on-screen messages and other features. However, a problem remains in defining how known camera and broadcast studio equipment operating in accordance with an 1125 line 60 Hz field rate format may properly interface with a high definition B-MAC television signal encoder so that the studio produced high definition signal may be transmitted over long distances without significant loss of high definition information. Furthermore, there is no particular discussion of how the disclosed high definition B-MAC television system will interface with other known possible input signal formats besides MUSE, such as 525 line 1:1 at a 59.94 Hz field rate or a 1050 line 2:1 signal operating at a 59.94 Hz field rate.
Consequently, there remains a requirement in the art for apparatus and a method of converting and preprocessing a studio produced high definition television signal into a signal for encoding via high definition B-MAC encoding techniques for transmission efficiently and without signal loss or degradation.